The Government has been accused of being "callous" after announcing that hundreds more disabled workers at Remploy factories are at risk of losing their jobs under fresh closure plans.

A further 875 employees, including 682 disabled people, have been told they face compulsory redundancy, some hearing the grim news by email. Unions attacked the decision as "cruel", warning of the difficulty disabled workers will face when they look for other jobs.

Ministers announced earlier this year that a number of Remploy factories would close, arguing that the budget for disabled employment services could be spent more effectively. Thirty-four factories have ceased operations since then and are in the process of closing, but the future of a further 18 sites remained unclear.

Some of the factories have the potential to move out of Government-funded support, but others are set to close, ministers said on Thursday. Workers at risk of redundancy are in 15 Remploy factories, with three automotive businesses not included.

Staff facing redundancy include those in an automotive textiles factory in Huddersfield, furniture business based in Neath, Sheffield and Blackburn, textiles based at Dundee, Stirling and Clydebank and packaging based at Norwich, Portsmouth, Burnley and Sunderland.

A Department for Work and Pensions spokesman said: "Our priority throughout this process is to safeguard jobs, which is why we are offering a wage subsidy of up to £6,400 per disabled employee to encourage interested parties to come forward.

"We have also been clear from the start that we have protected the £320 million budget for disability employment services. But we are following the advice of disability expert Liz Sayce, to use the money more effectively to get more disabled people into mainstream jobs - the same as everyone else. All disabled employees affected by the changes will be guaranteed tailored support from an £8 million package, including a personal case worker, to help with the transition into mainstream employment."

TUC general secretary Brendan Barber described it as a "heartless decision", saying: "Many of the disabled workers who will lose their job as a result of these factory closures have little or no chance of finding alternative employment. Of the first 1,000 employees to be made redundant during recent factory closures, just 35 have subsequently found work."

Shadow work and pensions secretary Liam Byrne said: "This is a shameful act from a contemptuous government. A day after the Autumn Statement in which the claimant count was revised up, David Cameron and Iain Duncan Smith (Work and Pensions Secretary) have thrown out of work almost 1,000 disabled workers."

The DWP disagreed with union estimates on how many Remploy workers had found other jobs, saying that 129 have found alternative work.